DE3823308A1 - METHOD FOR PRODUCING ORGANOSILANES - Google Patents

Description

The present invention relates to a new method for the production of organochlorosilanes by reaction of atomized silicon with an alkyl or aryl chloride in the presence of a copper catalyst and promoter sub punch. In particular, the invention relates to a method ren for the production of methylchlorosilanes.

The basic process for making methyl chlorosilanes is the direct implementation of fine particles ground silicon with methyl chloride in the presence of metallic copper or, more rarely, silver as a catalyst gate. The implementation is known to the person skilled in the art as "Rochow-Syn these "are known and described in US Pat. No. 2,380,995.

This process predominantly gives a mixture of the following silanes (Me = CH ₃ ): Me ₂ SiCl ₂ , Me ₄ Si, Me ₃ SiCl, MeSiCl ₃ , SiCl ₄ , HSiCl ₃ , MeHSiCl ₂ and Me ₂ HSiCl. In addition to the monomeric methylchlorosilanes mentioned, relatively high-boiling compounds such as methylchlorodisilanes, methylchlorotrisilanes, disiloxanes and silmethylenes are also formed in smaller amounts.

The monomeric compounds are mostly used industrially, including dimethyldichloro silane. This preferred reaction product is therefore aimed for with the highest possible selectivity: One measure of this is, among other things, the ratio of MeSiCl ₃ / Me ₂ SiCl ₂ (the so-called tri / di ratio), the value of which should be as small as possible.

The production is particularly interesting on an industrial scale of methylchlorosilanes by reaction of methyl chloride with silicon in a fluidized bed reactor, whereby in the over shot used methyl chloride both reactants as well as fluidization medium.

Since the basic research about 40 years ago to date it has a large number of publications given in which procedures to carry out the reak tion, to improve selectivity, to manufacture of suitable contact materials and catalyst / promoter systems are described. Summarize a first the overview can be found e.g. in "Organohalosilanes: Precursors to silicones ", Voorhoeve, Elsevier Publishing Company Amsterdam, New York, Londen, 1967.

Recent work has mainly focused on the targeted use of trace elements, so-called promo gates in the catalyst system.

Examples include: DE-A-34 25 424, EP-A- 1 38 678, EP-A-1 38 679, DE-A-35 01 085, EP-A-1 91 502, EP-A-1 94 214, EP-A-1 95 728, EP-A-2 23 447.  

Comparatively few publications refer on the silicon and if so, then there are purity requirements or physical parameters such as grain sizes distribution subject of work. For example be U.S. Patent No. 31,333,109 writes that part sizes from 20 to 200 µm for optimal operation a fluidized bed reactor are suitable. In U.S. Patent No. 45 00 724 silicon smaller than 700 µm is suitable viewed, the average grain size 20 to 300 microns and should preferably be 100 to 150 microns. The above mentioned limits are generally considered to be state of the art and experts know that the respective optimum in narrow Connection with the reactor system used in each case see is.

The present invention now includes a method for the production of organochlorosilanes, which thereby is characterized in that silicon is produced by atomization or a suitable alloy of silicon made by Has been manufactured, used and so in one for the production of organochlorosilanes directly insertable fine-particle shape has been brought.

The atomization of metals (in English: atomizing) is a common manufacturing process of metal powders and finds z. B. with metals like Copper or its alloys have been in use for a long time.  

Metal powders produced in this way are usually manufactured according to the in to powder metallurgy usual working techniques Process molded parts with special properties works; see also: Ullmann's Encyclopedia of tech African chemistry, 4th edition, volume 19, spec. P. 566, Verlag Chemie, Weinheim, 1980.

What is decisive with atomization technology is that extremely short solidification and cooling times for that Silicon can be realized.

Completely surprising and new is the fact that starting material thus produced at the organochlor silane synthesis much higher reaction speed ten shows.

The inventive method is in the case of methyl chlorosilane synthesis carried out in such a way that atomized silicon with a purity of more than 98.5% and a grain size of less than 500 µm with methyl chloride, in the presence of a mechanical produced mixture of copper catalyst and Pro engine substances. The invention preferably comes Process in a fluid bed reactor for use because here the far cheapest expansions of desired Product received and also procedural niche advantages, e.g. high heat transfer, who uses that can.  

Another preferred embodiment of the method is the implementation of a silicon / copper alloy that was also obtained by atomization, with methyl chloride.

So-called. Promoter elements, provided they are in metallic form can of course also be used be added to the alloy to be atomized or else the atomized silicon / copper alloy also mechanically be added.

Also in the latter case comes in the implementation the reaction preferably a fluidized bed reactor for Commitment.

The silicon used in the process according to the invention has a purity of more than 98.5% Si, preferably more than 99% Si. Particular emphasis is placed on the Pb content of the silicon not exceeding 10 ppm. Since the preferred process engineering embodiment of the present invention is the implementation in a fluidized bed reactor, in addition to the chemical properties of silicon, physical properties , such as particle size distribution , are of considerable importance. The silicon particles should generally be less than 500 μm, a grain size distribution between 30 and 300 μm with an average grain size of 100 to 150 μm is preferred.

The limits given above for the preferred part Size distribution are also suitable for a suitable gloomy silicon / copper alloy valid.

In the preferred embodiment of the invention process for the preparation of methylchlorosilanes 0.5 to 8 parts of catalyst / promoter mixture 100 parts of silicon metal and preferably 1 to 3 parts the mixture used on 100 parts of silicon. This However, the range can vary widely as the Implementation usually not discontinuously, but continuously carried out in a fluidized bed reactor becomes.

According to the invention, an atomized alloy comes into play sentence, the composition here is as follows chooses:

Si: 90 to 99% by weight
Cu: 0.5 to 8% by weight

Of course, both an atomized alloy as well as atomized silicon itself be the expert knew typical impurities such as Fe, Al, Ca, Ti etc. included.

According to the invention, the melt still to be atomized ze add suitable promoter elements. Promoter elements are known to those skilled in the art and it should be the one here literature cited above. In particular called the elements zinc, tin and phosphorus there.  

The process according to the invention is carried out at one temperature in the range from 250 to 350 ° C, but preferably between between 280 and 330 ° C.

It is recommended to face the procedure below Atmospheric pressure to perform increased pressure, as a result the space / time yield is increased.

An overpressure of up to 10 bar is advisable up to 5 bar.

The selectivity is important under these conditions Lich the formation of dimethyldichlorosilane optimal. In addition, a process engineering is optimal controllable reaction speed achievable.

The gaseous methyl chloride is converted into large excess used since it is continuously through the Contact mass made of silicon metal grains and the Kataly sator / promoter mixture or by the atomized alloy tion is passed through and this fluidized.

The person skilled in the art knows that especially in the laboratory rium scale not necessarily ar with fluid bed reactors must work, rather reactors often come here Use where the contact mass during the implementation vibrated or with a spiral stirrer is kept moving to prevent local overheating avoid and ensure a safe response Afford.  

Like the numerous publications cited above have been tried so far in addition to selectivity also the yield of dimethyldichlorosilane via the kata Improve lysator / promoter system. Everything was found However, the reaction speed is also very sensitive bel reacted to promoters and inhibitors. So is in DE-OS 34 25 424 on p. 10 the considerable increase the rate of formation of dimethyldichlorosilane with have been made the subject of the invention.

It was all the more surprising that the type of comminution of the silicon - atomizing versus grinding - also plays such a decisive role. This effect is surprising and new.

The method according to the invention can of course also be used Manufacture of other organochlorosilanes used will. Changes that may become necessary Process parameters are familiar to the person skilled in the art.

In the following the invention is illustrated by examples explained in more detail:

example 1

In a glass stirred-bed reactor, inner diameter = 30 mm, which is equipped with a spiral stirrer, all of the following experiments were carried out. Here the same amount of silicon or silicon / Copper alloy with the same grain size from 71 to 160 µm used. Methyl chloride was under pressure from 2 bar from below through a glass frit through the con clock mass directed. The amount of methyl chloride was kon kept constant and was approx. 1.5 l / h in all cases at 2 bar. After heating and starting the reak tion was a stationary test phase at 300 ° C and the quantity under such defined conditions determined per unit time of crude silane mixture formed. The specified values are always the average of four Individual determinations under constant boundary conditions conditions of: 2 bar, 1.5 l / h methyl chloride and 300 ° C.

The contact mass consisted of 40 g silicon, 3.2 g copper catalyst and 0.05 g ZnO and was before Use homogenized. In all cases it was the same Catalyst used. Sample A and B are on usual Commercially available silicon produced by milling powder of different provenance. Sample C is a silicon powder produced by atomization.

Under comparable reaction conditions (2 bar, 1.5 l / h MeCl and 300 ° C) you can find the following production rates given in g / h raw silane mixture:  

A: 5.7 g / h; B: 5.2 g / h; C: 8.3 g / h;

that corresponds to an increase in the production rate of approx. 45 or 56% through the use of atomized mate rial.

In the following, the Si licium powder the main impurities (wt .-%) as well those at the above Reactor runs achieved selectivities, expressed by the ratio of methyltrichlorosilane to dimethyldichlorosilane (T / D), reproduced:

Example 2

In the reactor described in Example 1 was under the same conditions (2 bar, 1.5 l / h methyl chloride, 300 ° C) an alloy made by atomization fol gender composition reacted:

Fe: 0.34; Al: 0.40; Cu: 5.75; Zn: 0.14
(plus other non-analyzed impurities)

The production rate found was two Experiments with 8.13 g / h and 9.4 g / h also clearly above usual production rates of 5 to 6 g / h.  

Example 3

Example 3 is intended to show that the rapid cooling of ent is of crucial importance for the production rate.

Among the above Reaction conditions will be those in example 1 sample named under C compared to a sample D of the same atomizing material, which however is use in the direct synthesis of an annealing treatment has undergone. The sample was placed in an ampoule melted in a vacuum, annealed at 1000 ° C for 2 h and then slowly again over a further 6 to 8 hours cooled down.

With the above Reaction conditions for the implementation with Methyl chloride can be found (see Example 1) the following pro production rates:

Sample C (uncannealed): 8.3 g / h
Sample D (annealed): 2.35 g / h

The composition of the contact mass was self ver always chosen the same.

The example shows a decrease in the production rate for raw silanes to about 28% compared to the original Sample C, which is exclusively for heat treatment is due.

Claims (3)

1. A process for the preparation of organochlorosilanes by reacting silicon and / or silicon alloys with alkyl and / or aryl chlorides in the presence of a copper catalyst and optionally promoter substances, characterized in that atomized silicon and / or an atomized silicon alloy is used. 2. The method according to claim 1, characterized in that that an atomized Si / Cu alloy is used. 3. The method according to claim 1 or 2, characterized records that the atomized silicon or ver atomized Si alloy already promoter elements ent holds.